Studies were undertaken to measure the electron-relaxation time of copper in solution. Progressive saturation measurements were done using a high efficiency loop-gap resonator. Problems arose because of sample heating. The microwave bridge of the Bruker ER200 ESR spectrometer was modified to include a 500 mW power amplifier, and a microwave switch was used to gate the microwave power incident on the resonator. The duty cycle of the microwave power was decreased as the level of power increased. In this way, it was possible to keep the average incident power and, therefore, the heating constant. Measurements of copper acetylacetonate in chloroform and chloroform-paraffin oil mixtures were made as a function of mixture ratio and temperatures. It was possible to obtain a measurement of the reaction time of copper in a solution for the first time. The measured relaxation times ranged from about a nanosecond at room temperature in chloroform to about 30 nanoseconds in mixtures at lower temperatures. The data are being analyzed to investigate the contributions of various mechanisms to relaxation.